Submission #1232306

#	Time	Username	Problem	Language	Result	Execution time	Memory
1232306		tdiv	Mobile (BOI12_mobile)	C++20	100 / 100	533 ms	8276 KiB

mobile

#include<bits/stdc++.h>
using namespace std;

#define TASK ""

#define FOR(i,a,b) for (int i = (a); i <= (b); ++i)
#define FOr(i,a,b) for (int i = (a); i <  (b); ++i)
#define FOD(i,a,b) for (int i = (a); i >= (b); --i)
#define FOd(i,a,b) for (int i = (a); i >  (b); --i)
#define ll long long
#define ii pair<int, int>
#define all(x) (x).begin(), (x).end()
#define pb push_back

const int MAX = 1002207;
const int MOD = (int)1e9 + 7;

struct point {

    int x, y;

    void refine(void) {
        y = abs(y);
    }

    friend istream &operator >> (istream &ifs, point &p) {
        return ifs >> p.x >> p.y;
    }

};

int n, L;
point arr[MAX];

bool check(double r) {
    stack<pair<double, double>> st;

    for (int i = 1; i <= n; ++i) {
        auto &[x, y] = arr[i];
        if (y > r) continue;
        double d = sqrt(r * r - (double)y * y);
        double dx1 = x - d, dx2 = x + d;

        while (!st.empty() && st.top().second >= dx1) {
            dx1 = min(dx1, st.top().first);
            dx2 = max(dx2, st.top().second);

            st.pop();
        }

        st.push(make_pair(dx1, dx2));
    }

    double reach = 2e9;

    while (!st.empty() && reach > 0.0000000) {
        auto &[x1, x2] = st.top();
        st.pop();
        if (x2 >= (double)L) {
            reach = x1;
            continue;
        }
        if (reach > x2) return false;
        reach = x1;
    }

    return reach <= 0.00000000;
}

void waguri(void) {
    cin >> n >> L;
    FOR(i, 1, n) {
        cin >> arr[i];
        arr[i].refine();
    }

    double lo = 0, hi = 2e9;
    double mid;

    FOR(t1, 1, 100) {
        mid = (lo + hi) / 2.00;
        if (check(mid)) {
            hi = mid;
        }
        else lo = mid;
    }
    
    mid = (lo + hi) / 2.000;

    cout << fixed << setprecision(6) << mid << "\n";

    return;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    if (fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }

    int tt;
    tt = 1;
    while (tt--) {
        waguri();
    }
    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:99:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   99 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mobile.cpp:100:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  100 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
• Subtask 6: 5 / 5
• Subtask 7: 5 / 5
• Subtask 8: 5 / 5
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• Subtask 10: 5 / 5
• Subtask 11: 5 / 5
• Subtask 12: 5 / 5
• Subtask 13: 5 / 5
• Subtask 14: 5 / 5
• Subtask 15: 5 / 5
• Subtask 16: 5 / 5
• Subtask 17: 5 / 5
• Subtask 18: 5 / 5
• Subtask 19: 5 / 5
• Subtask 20: 5 / 5
• Subtask 21: 5 / 5